Human papillomaviruses (HPVs) are believed to be important in the etiology of oral cancer. They are present in many of the tumors and can transform oral epithelial cells to a malignant phenotype. In the current grant period we have developed ribozymes which cut the RNA transcript of HPV-18, and which inhibit the malignant phenotype of a cervical cancer cell line that expresses HPV-18. In the next grant period we will expand upon this work to achieve three aims. Specific Aim 1 will be to broaden the spectrum of anti-HPV ribozymes. This will be done by making new ribozymes that inhibit HPV that are found in over 60% of oral cancers. A virus vector will be made which expresses all three of the ribozymes in a single construct. The functions of this multi-ribozyme vector will be opitmized so as to express the strongest anti-HPV activity. Specific Aim 2 will be to use the ribozymes to study the role of HPVs in the growth of oral cancer cells. A large panel of oral cancer cells and other cells will be examined. We will test the hypothesis that the HPVs express the viral E6 and E7 proteins, which in turn block the activity of the cellular p53 and RB proteins, thus preventing programmed death of the cancer cells. Specific Aim 3 will be to find if the anti-HPV ribozymes are active as gene therapy agents against oral cancer. Oral cancers will be removed from patients and transplanted to nude mice. There they will be treated with the virus vector that express anti-HPV ribozymes. The anti-cancer effects will be used to predict the effects of this form of gene therapy on patients with oral cancer. This project will answer basic questions regarding the etiology of oral cancer and will contribute to the development of new treatments.